Separation of cobalt from nickel and cobalt bearing ammoniacal solutions

ABSTRACT

A process for extracting a nickel product having a predetermined nickel to cobalt ratio and a mixed nickel-cobalt sulphide product having a low nickel to cobalt ratio from reduced nickel and cobalt bearing lateritic and garnieritic ores. The reduced ores are leached in one or more stages under oxidizing conditions in an aqueous ammoniacal ammonium carbonate solution. Solution from the leaching operation is treated in a multi-stage cobalt removal operation in which excess sulphidizing agent is added to one stage to effect extraction of a large quantity of cobalt from solution as a mixed nickel-cobalt sulphide precipitate. The amount of sulphidizing agent added to another stage is restricted to produce a mixed nickel-cobalt sulphide precipitate with a low Ni:Co weight ratio. The mixed sulphide precipitate is removed from each stage solution and a portion is recycled to the solution from which it was removed.

Unite States Patent [191 Weir et al.

[ 1 Feb. 13, 1973 [54] SEPARATION OF COBALT FROM NICKEL AND COBALTBEARING AMMONIACAL SOLUTIONS [7 51 Inventors: Donald Robert Weir;Russell Peter Kofluk, both of Fort Saskatchewan, Alberta, Canada [73]Assignee: Sherritt Gordon Mines Limited,

Toronto, Ontario, Canada [22] Filed: March 24, 1971 [21] AppL No;127,677

[52] U.S. Cl. ..423/l43, 423/140, 75/103, 75/119 [51] Int. Cl ..C0lg51/00, COlg 53/00 [58] Field of Search ...75/103, 119; 23/134; 423/143,423/140 [56] References Cited UNITED STATES PATENTS 2,693,404 11/1954Mackin ..7S/l19 X 2,013,334 11/1959 Dean ..75/1 19 X FOREIGN PATENTS ORAPPLICATIONS 811,078 4/1969 Canada ..75/119 717,474 9/1965 Canada,.'..7S/1l9 Primary ExaminerHerbert T. Carter AttorneyFrank l. Piper,Arne l. Fors and James T.

Wilbur [57] ABSTRACT A process for extracting a nickel product having apredetermined nickel to cobalt ratio and a mixed nickel-cobalt sulphideproduct having a low nickel to cobalt ratio from reduced nickel andcobalt bearing lateritic and gamieritictores. The reduced ores areleached in one or more stages under oxidizing conditions in an aqueousammoniacal ammonium carbonate solution. Solution from the leachingoperation is treated in a multi-stage cobalt removal operation in whichexcess sulphidizing agent is added to one stage to effect extraction ofa large quantity of cobalt from solution as a mixed nickel-cobaltsulphide precipitate. The amount of sulphidizing agent added to anotherstage is restricted to produce a mixed nickel-cobalt sulphideprecipitate with a low Ni:Co weight ratio. The mixed sulphideprecipitate is removed from each stage solution and a portion isrecycled to the solution from which it was removed.

7 Claims, 3 Drawing Figures SEPARATION OF COBALT FROM NICKEL AND COBALTBEARING AMMONIACAL SOLUTIONS This invention relates to the separation ofnickel and cobalt from solutions derived from leaching nickel and cobaltbearing material, such as reduction roasted laterite ore, in ammoniacalammonium salt solutions. More particularly, the invention is directed toa process for treating such solutions to retain a maximum amount of thenickel content in the solution while separating a maximum amount of thecobalt as a mixed nickelcobalt sulphide precipitate containing a minimumamount of nickel.

It is known that nickel and cobalt values can be ex- 'tracted fromvarious nickel and cobalt bearing materials by hydrometallurgicalmethods, such as by leaching with ammoniacal ammonium carbonate orammonium sulphate solutions, It is also known that cobalt and copper canbe precipitated from an ammoniacal ammonium salt solution which containsdissolved salts of nickel, cobalt and copper by reacting the solutionwith a sulphidizing agent which combines first with the dissolved coppervalues, then the cobalt values and converts them to insoluble copper andcobalt sulphides which precipitate from the solution. Sulphidizingagents which have been found particularly suitable for this purposeinclude H 8, (NHQ S, Na,S and NaHS.

A sulphidizing agent is only partially successful to preferentiallyprecipitate cobalt from an ammoniacal ammonium salt solution containingdissolved nickel and cobalt values. A significant proportion of thedissolved cobalt values remains in solution and either contaminates theproduct nickel subsequently recovered from the solution or becomes lost.Moreover where the nickel to cobalt ratio in solution is relatively highe.g., 2:1 or more, the sulphidizing agent causes nickel to precipitatein an amount approximately equal to or greater than the amount ofprecipitated cobalt. The nickel precipitated with the cobalt representsan appreciable loss since the value of nickel in a mixed nickel-cobaltsulphide precipitate is much less than the value of product nickelrecovered from the solution.

The cobalt content of the solution can be decreased to a very low levelby adding sulphidizing agent in large excess over the theoretical amountnecessary to precipitate all cobalt. However the sulphidizing agentcauses a large proportion of the nickel in solution to coprecipitatewith the cobalt in the form of a mixed nickel-cobalt sulphide. Wheresufficient sulphidizing agent is added to the solution to produce avaluable solution containing dissolved nickel but little dissolvedcobalt, the proportion of nickel recovered from the feed ore reportingin the solution is much smaller than the proportion of nickel reportingin the mixed nickelcobalt sulphide. For example, where it is desired torecover nickel from a solution derived from a reduced lateritic andgarnieritic ore and sulphidizing agent is added in amount sufficient toincrease the nickel'to cobalt ratio to 500:], the lowest desirable ratiofor most practical applications, the nickel to cobalt ratio of the mixedsulphides will be relatively high, generally considerably above 4:1

The present invention contemplates a process for obtaining a solutionhaving a high nickel to cobalt ratio, generally 700:1 or higher whilemaintaining the ratio of nickel to cobalt in the mixed cobalt-nickelsulphide precipitate at a low value, generally 2:1 or considerablylower. Where the starting solution contains in addition to nickel andcobalt, copper values, the invention also contemplates a solution whichis substantially free of copper and a mixed sulphide precipitatecontaining substantially all copper values.

Briefly stated, the process which meets these objectives involves amulti-stage cobalt removal procedure in which one stage is controlled toeffect removal of a required amount of cobalt from solution to produce aproduct liquor having a predetermined dissolved nickel to cobalt ratio.The conditions can be adjusted to achieve a product liquor having apredetermined nickel to cobalt ratio generally 70021 or higher, or wherea product liquor having such a high nickel to cobalt ratio is notrequired e.g., where the solution is subjected to hydrogen reduction forextraction of nickel values, the conditions may be adjusted to achieve aliquor having a NizCo ratio less than 700:1. The conditions in anothercobalt removal stage are controlled to produce a mixed nickel-cobaltsulphide precipitate of predetermined nickel-cobalt weight ratio.Usually the conditions are adjusted to achieve a nickel to cobalt ratioin the precipitate of less than 2:1. The solution from thefirstmentioned cobalt removal stage having a high nickel to cobalt ratiois recovered as product liquor for subsequent treatment for recovery ofnickel and the low nickel-cobalt ratio mixed sulphide precipitate fromthe second-mentioned cobalt removal stage is recovered as product mixedsulphide precipitate. The mixed sulphide precipitate having a highnickel-cobalt ratio from the firstm'entioned cobalt removal stage isrecycled partly to the first-mentioned cobalt removal stage and theun-recycled portion is fed to the second-mentioned cobalt removal stage.The solution from the secondmentioned cobalt removal stage is recycledto the leaching operation from whence the nickel and cobalt bearingammoniacal ammonium salt solution is derived. The effect of theforegoing procedure is that only the desired solution of predeterminednickelcobalt ratio and the mixed sulphide precipitate of predeterminednickel-cobalt ratio are recovered while the solution from which theproduct precipitate is recovered and the precipitate removed from theproduct solution are re-circulated within the system. Thus theconditions in the cobalt removal stages can be controlled to achieve asolution and precipitate of any given nickel to cobalt ratio. If thestarting solution also contains dissolved copper values substantiallyall of these values are precipitated by the sulphidizing agent andreport with the mixed sulphide precipitate.

The recycled mixed sulphides serve to reduce dissolved cobalt to acobaltous state in which form it is selectively precipitated withconsumption of less sulphidizing agent. The cobalt content of thesolution can be decreased to an extremely low level in thefirst-mentioned cobalt removal stage by careful control of the quantityof sulphidizing agent added to solution to produce liquor having anickel to cobalt ratio of a required value. According to the process theconditions can be adjusted to achieve a ratio well in excess of 700:1.The resulting mixed sulphide precipitate may have a relatively high,e.g., 8:1 or more, nickel to cobalt ratio but this is not a problemsince this precipitate is recycled to the first and second-mentionedcobalt removal stages where replacement of nickel with cobalt in themixed sulphide precipitate occurs. The Ni/Co ratio of the final mixednickel-cobalt sulphide precipitate from the second-mentioned cobaltremoval stage may be controlled at a low level through control of thequantity of sulphidizing agent used in that stage.

The process of this invention is described in detail below withreference to the accompanying drawings in which:

F108. .1, 2 and 3 are flow-schemes of three specific processesincorporating the improvement of the present invention.

The process described herein may be employed in conjunction with anyoverall process for recovering nickel and cobalt from source materialsby leaching with ammoniacal ammonium salt solutions. However, theinvention is particularly well adapted for use in conjunction withprocesses for recovering nickel and cobalt from lateritic andgarnieritic ores by reduction roasting and ammonium carbonate leaching.Such processes are described in detail in a number of publications,including Canadian Pat. Nos. 811,078 and According to the process, theore is dried to reduce the moisture content to below about 5 percent byweight, then ground to substantially 100 percent minus 100 mesh standardTyler screen. The ore is fed into the top of a multiple-hearth furnace,passes downwardly and counter-currently to hot reducing gases and exitsfrom the bottom. The ore is initially preheated in the furnace to about500 C. then reduction roasted at a temperature of about 500 to 850 C.During the reduction roasting operation, the nickel and cobalt oxides inthe ore reduce to metallic form. The conditions in the furnace arecontrolled to minimize the amount of iron which reduces to a solubleform.

The reduced ore discharged from the furnace is cooled then treated withan aqueous ammoniacal ammonium carbonate solution to extract themetallic nickel and cobalt values and dissolve them in the leachsolution as nickel and cobalt ammine carbonate. The leach operation isusually conducted in two stages. Solution and residue from the firststage leach are separated and the residue is passed to the second stageleach. A portion of the solution decanted from both leach stages isrecycled to the leach stage from which the solution is decanted and theremainder is treated with a sulphidizing agent which precipitates alarge proportion of cobalt and a lesser proportion of nickel from thesolution. The sulphidizing agents include ammonium sulphide, hydrogensulphide, sodium sulphide and sodium sulfhydrate.

The precipitate which comprises a mixed cobaltnickel sulphide isseparated from solution and the solution is passed to treatment for therecovery of the nickel values.

The present invention departs from the foregoing process by conductingthe cobalt removal in two stages and recycling a portion of the mixedsulphide precipitate, freshly precipitated from each cobalt removalstage to the stage from which the precipitate was removed. The residueis effective in reducing dissolved cobalt in the cobaltic state tocobaltous cobalt thereby improving the preferential precipitation ofcobalt by the sulphidizing agent. Also, the nickel in the high nickelprecipitate is redissolved and replaced by cobalt to yield a precipitateof low nickel to cobalt ratio.

The sulphidizing agent added to the cobalt removal stages may beammonium sulphide, hydrogen sulphide, sodium sulphide and sodiumsulfhydrate.

In the scheme shown in FIG. 1, a single stage leach with two cobaltremoval steps is employed. In general this scheme is satisfactory whenthe nickel content of the ore is relatively high. Solution from leachstep 10 is separated from leach residue in thickener 12 and the residueis washed with ammonium carbonate make up solution in washing step 14.The wash solution is recycled to the quenching or leach slurry makeupstep 16. The leach solution from thickener 12 is passed to retentioncell 18 in which it is stirred thence is passed to first stage reactor20 where a sulphidizing agent is added. The mixed nickel-cobalt sulphideprecipitate is separated from solution in thickener 22 and a portion isrecycled to retention cell 18. The remainder is filtered at 24 andsolution is recycled to quench 16. The filter is washedwith ammoniacalammonium carbonate solution at washing step 25. It is believed contactof the mixed nickel-cobalt sulphides with the ammoniacal solution atthis stage causes a portion of the nickel values to redissolve intosolution thereby diminishing the nickel to cobalt ratio of the mixedsulphide product. The washing step 25 is an optional but a preferredoperation in the overall flow scheme. Solution from step 25 is recycledto washing step 14.

Part of the overflow from thickener 22 is passed to retention cell 26 ofthe second cobalt removal stage, and the remainder is passed to quench16. Material from cell 26 is passed to reactor 28 and a large quantityof sulphidizing agent is added thereto in order to strip out most of thecobalt in solution. Accordingly, the solution in reactor 28 has a highnickel to cobalt ratio. The residue is separated from solution inthickener 30 and a portion is recycled to retention cell 26. Theremainder of the sulphide residue is passed to retention cell 18. Thesolution from thickener 30 is passed to post-precipitation step 31 inwhich the solution is maintained at a temperature of about 65 to 70 C.for a period of time, generally about 10 minutes. The postprecipitationstep results in precipitation of trace sulphides and manganese valuesboth of which may be removed by filtration leaving a product liquorhaving a high nickel to cobalt ratio. The post-precipitation step is anoptional but preferred operation in the flow scheme.

FIG. 2 illustrates a two-stage leach and two-stage cobalt removaloperation. Solution and residue from the first stage leach 32 areseparated in thickening step 34 and residue is repulped at 36 insolution from washing operation 38. The repulped residue is passed tothe second stage leach 40 and residue from the leaching operation isseparated from solution in thickening step 42 and passed to washingoperation 38. Part of the solution from thickener 34 is passed toretention cell 44 in which it is stirred thence passed to first stagereactor 46 where a sulphidizing agent is added. Solution is separatedfrom the mixed cobalt-nickel sulphide precipitate in thickener 48 andthe solution is passed to post-precipitation step 49. A portion of theprecipitate is recycled to retention cell 44 and the remainder joins thestream of solution from thickeners 42 and 34 flowing to retention cell50. The solution is stirred in cell 50 thence is passed into secondstage reactor 52 to which sulphidizing agent is added. Residue andsolution from reactor 52 are separated in thickener 54 and solution isrecycled to quenching step 56. Part of the underflow from thickener 54is recycled to cell 50 and the remainder is filtered at 58. Solutionfrom step 58 is recycled to quench 56. The filter cake is washed withammoniacal ammonium carbonate solution in washing step 59 and theresidue forms the mixed sulphide product. Solution from washing step 59is recycled to wash 38.

The filtrate from post-precipitation step 49 forms the product liquor ofhigh nickel towcobalt ratio and a mixed sulphide precipitate having alow nickel to cobalt ratio is obtained from washing step 59.

The conditions in the first stage reactor 46 are adjusted so that theproduct liquor has the required nickel to cobalt ratio (generally in theorder of 700:1 or higher) and the conditions in the second stage reactor52 adjusted so that the mixed sulphides product has a low nickel tocobalt ratio (generally in the order of 2:1 or less).

To obtain a product liquor having a high nickel to cobalt ratio in thefirst stage reactor, sufficient sulphidizing agent and recycled mixedsulphide precipitate must be provided in the reactor to precipitatesubstantially all cobalt in solution as a sulphide. Sulphidizing agentmust be provided in the solution in a quantity sufficient to yield asulphide to cobalt molar ratio usually between about 3.0 to about 10.0or even higher. In solutions to which the mixed sulphide precipitate isrecycled, sufficient amount of the precipitate must be recycled toensure substantially complete reduction of trivalent cobalt to thecobaltous state.

Where the conditions in the first stage reactor 46 are so adjusted, asignificant proportion of the dissolved nickel will co-precipitate withthe cobalt. The mixed sulphide precipitate has a nickel to cobalt ratioconsiderably higher than derived in the nickel cobalt sulphides. Thenickel value in the precipitate is not however permanently lost to theproduct liquor.

Nickel in the portion of the precipitate recycled to the first stagereactor is replaced by cobalt and the nickel redissolve's into solution.Nickel in the portion of the precipitate passed to the second stagereactor is also replaced by cobalt and the dissolved nickel is separatedfrom precipitate in thickener 54 and passes to quench 56. Ultimately,the redissolved nickel joins the product liquor in reactor 46.

In order to obtain a mixed sulphide precipitate having a low nickel tocobalt ratio from the underflow from thickener 54, the conditions in thesecond stage reactor 52 must be adjusted to precipitate the cobaltvalues in solution while suppressing the co-precipitation of nickelvalues. Accordingly, the amount of sulphidizing agent introduced intoreactor 52 must be severely restricted. The specific amount ofsulphidizing agent introduced into the reactor will depend onoperational conditions and other factors but in general the sulphide tocobalt molar ratio used in the reactor must be less than 3.0, preferablyas close to zero as possible consistent with the amount of cobalt whichit is desired to remove.

The amount of mixed sulphide precipitate passing from thickener 48 intoretention cell 50 need not be restricted as the sulphide value in theprecipitate is bound to contain cobalt and nickel and will not act toprecipitate nickel from the solution in reactor 52.

It should be noted that the nickel-cobalt ratio of the mixed sulphideproduct from the second stage cobalt removal circuit depends upon thecobalt content of the material treated in the first stage leach 32 aswell as the cobalt content of the product liquor. As the nickelcobaltratio of the mixed sulphides decreases, the cobalt content in the firststage leach 32 and the first stage reactor 46 increases proportionately.In order to obtain a product liquor having a high nickel: cobalt ratio,a large excess of sulphidizing agent must be added to the first stagereactor but in so doing the nickel: cobalt ratio produced in the secondstage reactor 52 of the mixed sulphides will be increased. However, bycareful control of the cobalt content of the streams running to bothfirst and second stage reactors and from thickener 54 to quench 56, amixed sulphide of required nickel: cobalt ratio can be obtained. Wherefor example the quantity of sulphidizing agent added to second stagereactor 52 is severely limited, the streams of liquid passing fromthickener 54 to quench 56 will have a relatively high cobalt contentthereby increasing the cobalt concentration in the first stage leach 32.As a result the nickel: cobalt content of the mixed sulphide precipitatewill decrease Similarly the amount of high cobalt sulphides recycled tothe first stage reactor can be increased to achieve the same result.

The process depicted in FIG. 3 is the same as that illustrated in FIG. 2except that the two stage cobalt removal scheme illustrated in FIG. 1 issubstituted for the first cobalt removal operation of FIG. 2. In generalthis scheme is satisfactory when the nickel to cobalt ratio of the oreis relatively low. This process has the advantage of a greater number ofstreams of solution than the schemes illustrated in FIGS. 1 and 2. Thusthere is greater flexibility in the ways in which the cobaltconcentrations in the leach solutions and cobalt removal reactors can beadjusted in order to achieve product liquor and precipitate of a desirednickel to cobalt ratio.

According to the process of FIG. 3, the overflow from first stagethickener 60 is passed to retention cell 62 of the initial cobaltremoval stage. The overflow from the thickener 64 of the initial cobaltremoval state is passed to the intermediate stage retention cell 66 andthe underflow from thickener 64 is passed partly to final stageretention cell 68 and the remainder is recycled to cell 62. The overflowfrom the intermediate stage thickener 70 is passed to post-precipitationstep 71 and the solution therefrom forms the product liquor. A portionof the underflow from thickener 70 is passed to cell 62 and the balanceis recycled to cell 66.

Feed to final stage cell 68 includes the overflow from the second leachstage thickener 72 as well as part of the overflow from thickener 60 andunderflow from initial cobalt removal thickener 64. The overflow fromfinal cobalt removal thickener 74 is passed to quench 76. The underflowis passed to filter 78 and the solution is passed to quench 76. The cakeis washed at 80 and the washed residue forms the mixed sulphide produce.The wash liquor is passed to leach residue wash 82.

EXAMPLE This example illustrates the operation of the two stage cobaltremoval process according to the flow scheme illustrated in FIG. 2.Where reference numerals are used, the operation or element designatedby the reference numeral performs or serves the same operation as theoperation or element designated by the same numeral.

The ore fed to quench step 56 was a reduced nickeliferous laterite orecontaining in addition to reduced nickel and cobalt, copper, iron,sulphur, aluminum, magnesium, manganese and chromium values. The firststage leach solution from thickener 34 containing (gm/l) 12.7-Ni,0.293-COT (total cobalt being made up to 0.028 gm/l Co-l-F and 0.265gm/l Co-ll+-) l12NH and 50.7CO was fed at the rate of 37.5 ml/minthrough three series-connected retention cells 44. Magnetic stirrers ineach cell kept the solution continuously in motion.

From the last retention cell the solution was fed at the rate of 40.95mls/min to a first stage pipe-line reactor (a pigtail condenser) 46maintained at a temperature of 30 C. (NH S was injected at the rate of0.80 ml/min into the reactor at the point of entry of the solution fromthe retention cell 44 and additional (NHQ S was injected at the rate of0.80 ml/min into the reactor at the point of entry of the solution fromthe retention cell 44 and additional (NH S was injected at the rate of0.20 ml/min at the end of the pipe-line. From the reactor the solutionwas passed to a retention cell in which sufficient time was allowed toconvert dissolved cobalt to a sulphide form. The solution was thenpassed to a 1,000 ml thickener 48.

Underflow from thickener 48 was withdrawn at the rate of 6.90 ml/min andone-half was recycled to retention cell 44. The remainder of thethickener underflow joined the stream of solution flowing from thesecond stage leach thickener 42 to retention cell 50. Overflow from thethickener 48 forms the substantially cobaltfree product liquor.

Second stage leach solution from thickener 42 containing (gm/l) 9.84-Ni,0.294-COT (0.021 Co-l-land 0.273 Co+++) 105-Nl-l and 46.9 C0, togetherwith the portion of underflow described above from thickener 48 was fedat the rate of 190 ml/min to two series-connected cells 50. Theretention time in the cells was 10.8 mins. Solution from the cells wasdischarged into a second stage pipe-line reactor 52. 1.56 ml/min (NH Swas injected into the reactor at the point of entry of the solution and0.2 ml/min was injected at the end of the pipe-line for the first fourhours of operation ofvthe scheme. From the fourth to sixth hours, therate of injection of (Ni-1.0 8 was increased to 2.00 mls/min at thepoint of entry and 0.41 mls/min at the end of the pipe-line. The liquidand solid discharged from the reactor was passed to a 550 ml cell andretained therein for 13.6 min. The material was then passed to a 6,000ml thickener 54. Overflow from the thickener was recycled to quench 56and the underflow was filtered at 58 and the residue was washed withammonium carbonate. The washed solids formed the product mixedsulphides.

Samples were taken at hourly intervals of the overflow from the firststage thickener 48 (designated A) and overflow (B) and underflow (C)from the second stage thickener 54. An analysis of these samples aretabulated below.

The results demonstrates that by recycling mixed cobalt-nickel sulphidesin a two stage sulphidizing operation, cobalt can be stripped to a verylow level from the product liquor and a mixed sulphide precipitate canbe obtained having a low NizCo ratio.

The NizCo ratio in the product liquor (solution from overflow A) after 1hour was 232021 and increased to 5690z1 after 3 hours. When the slurryis retained for a period of time after passage through reactor 46, thesulphidizing reaction will proceed to completion. The overflow fromthickener 48 is very clear and is not susceptible to post-precipitation.The Ni:Co ratio in the mixed sulphide precipitate (precipitate fromunderflow C) was less than one in every instance and well below thehighest desirable ratio of 2:1. The sulphides in the thickener overflow(B) represent less than 0.5 percent of the total quantity of sulphideprecipitate.

It will be understood, of course, that modifications can be made in thepreferred embodiments of the present invention as described hereinabovewithout departing from the scope and purview of the appended claims.

What we claim as new and desire to protect by Letters Patent of theUnited States is:

1. In a process for treating nickel and cobalt bearing material in whichthe material is subjected to a leaching operation in which it is leachedin one or more stages under oxidizing conditions with an ammonium saltleach solution in order to cause dissolution of nickel and cobalt valuescontained in said material after which said nickel and cobalt containingleach solution is separated from undissolved residue and said separatedsolution is subjected to a cobalt removal operation in which saidseparated solution is treated with a sulphidizing agent topreferentially precipitate cobalt values therefrom so as to provide aproduct liquor and a product precipitate composed of a mixednickelcobalt sulphide, said product liquor containing the bulk of thenickel values previously in said nickel and cobalt containing in whichit is leached in at least two stages under oxidizing conditions with anammonium salt leach solution in order to cause dissolution of nickel andcobalt values contained in said material after which said nickel andcobalt containing leach solution from each said leaching stage isseparated from undissolved residue and said separated solution from eachsaid leaching stage is subjected to a cobalt removal operation in whichsaid separated solu-tion is treated with a sulphidizing agent topreferentially precipitate cobalt values therefrom so as to provide aproduct liquor and a product precipitate composed of a mixednickelcobalt sulphide, said product liquor containing the bulk of thenickel values previously in said nickel and cobalt containing leachsolution together with a small residual quantity of cobalt, said productprecipitate containing the bulk of the cobalt values previously in saidnickel and cobalt containing leach solution together with a quantity ofco-precipitated nickel, the improvement to said cobalt-removal operationwhereby the nickelcobalt ratio in said product liquor is adjusted to avalue above about 700:1 concurrently with an adjustment of thenickel-cobalt ratio in said product precipitate to a value below about2:1, said improvement comprising the steps of: passing nickel and cobaltcontaining solution separated from one said leaching stage to a firstcobalt-removal stage to which is added sulphidizing agent in controlledamount such that the ratio of nickel to cobalt remaining in solutionfollowing formation of a mixed nickel-cobalt sulphide precipitatetherein is above about 700:1, removing solution from said firstcobalt-removal stage and recovery thereof as said product liquor forsubsequent treatment for recovery of nickel therefrom, removing fromsaid first cobaltremoval stage the mixed nickel-cobalt sulphideprecipitate formed therein and recycling at least a portion thereof tosaid first leach solution together with a small residual quantity ofcobalt, said product precipitate containing the bulk of the cobaltvalues previously in said nickel and cobalt containing leach solutiontogether with a quantity of co-precipitated nickel, the improvement tosaid cobalt-removal operation whereby the nickel-cobalt ratio in saidproduct liquor is adjusted to a value above about 700:1 concurrentlywith an adjustment of the nickel-cobalt ratio in said productprecipitate to a value below about 2:1, said improvement comprising thesteps of: passing said separated nickel and cobalt containing leachsolution to a first cobalt-removal stage to which is added sulphidizingagent in controlled amount such as to cause formation of a mixednickel-cobalt sulphide precipitate having a nickel-cobalt ratio of lessthan about 2:1, removing from said first cobalt removal stage the mixednickel-cobalt sulphide precipitate formed therein and recycling aportion thereof to said first cobalt removal stage and recovering theremainder thereof as said product precipitate, removing solution fromsaid first cobalt-removal stage and recycling a portion thereof to saidleaching operation and passing the remainder thereof to a second cobaltremoval stage to which is added sulphidizing agent in controlled amountsuch that the ratio of nickel to cobalt remaining in solution followingformation of a mixed nickel-cobalt sulphide precipitate therein is aboveabout 700:1, removing solution from said second cobalt-removal stage andrecovery thereof as said product liquor for subsequent treatment forrecovery of nickel therefrom, removing from said second cobalt-removalstage the mixed nickel-cobalt sulphide precipitate formed therein andrecycling at least a portion thereof to said second cobalt-removal stageand adding any unrecycled portion thereof to said first cobalt-removalstage.

2. The process as claimed in claim 1, wherein said product liquor ismaintained at a temperature of about 65 to C. for a time sufficient toprecipitate contained sulphides and any manganese thence saidprecipitated sulphides and any manganese are separated from solution.

3. The process as claimed in claim 1, wherein said mixed nickel-cobaltsulphide product is washed with ammonium carbonate and the wash solutionis recycled to the leaching operation.

4. In a process for treating nickel and cobalt bearing material in whichthe material is subjected to a leaching operation cobalt-removal stageand adding any unrecycled portion thereof to a second cobalt-removalstage, passing nickel and cobalt containing solution separated fromanother said leaching stage to said second cobaltremoval stage to whichis added sulphidizing agent in controlled amount such as to causeformation of a mixed nickel-cobalt sulphide precipitate having anickel-cobalt ratio of less than about 2:1, removing from said secondcobalt-removal stage the mixed nickel cobalt sulphide precipitate formedtherein and recycling a portion thereof to said second cobaltremovalstage and recovering the remainder thereof as said product precipitate,removing solution from said second cobalt-removal stage and recyclingthereof to said leaching operation.

5. In a process for treating nickel and cobalt bearing material in whichthe material is subjected to a leaching operation in which it is leachedin at least two stages under oxidizing conditions with an ammonium saltleach solution in order to cause dissolution of nickel and cobalt valuescontained in said material after which said nickel and cobalt containingleach solution from each said leaching stage is separated fromundissolved residue and said separated solution from each said leachingstage is subjected to a cobalt-removal operation in which said separatedsolution is treated with a sulphidizing agent to preferentiallyprecipitate cobalt values therefrom so as to provide a product liquorand a product precipitate composed of a mixed nickelcobalt sulphide,said product liquor containing the bulk of the nickel values previouslyin said nickel and cobalt containing leach solution together with asmall residual quantity of cobalt, said product precipitate containingthe bulk of the cobalt values previously in said nickel and cobaltcontaining leach solution together with a quantity of co-precipitatednickel, the improvement to said cobalt-removal operation whereby thenickelcobalt ratio in said product liquor is adjusted to a value aboveabout 700:1 concurrently with an adjustment of the nickelcobalt ratio insaid product precipitate to a value below about 2:1, said improvementcomprising the steps of: passing nickel and cobalt containing solutionseparated from one said leaching stage to a first cobalt-removal stageto which is added sulphidizing agent to cause formation of a mixednickel-cobalt sulphide precipitate therein, removing from said firstcobalt-removal stage the mixed nickel-cobalt sulphide precipitate formedtherein and recycling at least a portion thereof to said firstcobalt-removal stage and adding any unrecycled portion thereof to athird cobaltremoval stage, passing solution removed from said firstremoval state to a second cobalt-removal stage to which is addedsulphidizing agent in controlled amount Ill such that the ratio ofnickel to cobalt remaining in solution following formation of a mixednickel-cobalt sulphide precipitate therein is above about 700:1,removing solution from said second cobalt-removal stage and recoverythereof as said product liquor for subsequent treatment for recovery ofnickel therefrom, removing from said second cobalt-removal stage themixed nickel-cobalt sulphide precipitate formed therein and recycling atleast a portion thereof to said second cobalt-removal stage and addingany unrecycled portion thereof to said first cobalt-removal stage,passing nickel and cobalt containing solution separated from anothersaid leaching stage to said third cobalt-removal stage to which is addedsulphidizing agent in controlled amount such as to cause formation of amixed nickelcobalt sulphide precipitate having a nickel-cobalt ratio ofless than about 2:1, removing from said third cobaltremoval stage themixed nickel-cobalt sulphide precipitate formed therein and recycling aportion thereof to said third cobalt-removal stage and recovering theremainder thereof as said product precipitate, removing solution fromsaid third cobalt-removal stage and recycling thereof to said leachingoperation.

6. The process as claimed in claim 4 wherein said product liquor ismaintained at a temperature of about 65 to C. for a time sufficient toprecipitate contained sulphides and any manganese thence saidprecipitated sulphides and any manganese are separated from solution.

7. The process as claimed in claim 5 wherein said product liquor ismaintained at a temperature of about 65 to 75 C. for a time sufficientto precipitate contained sulphides and any manganese thence saidprecipitated sulphides and any manganese are separated from solution.

PatentNo, s no sis Date; February 13, 1973 Inventor) noun mosses wereET. AL.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shownbelow:

Cole 8 and 9, claim l should read as follows:

la In a process for treating nickel and cobalt bearing material in whichthe material is subjected to a leaching operation in which it is leachedin one or more stages under oxidizing conditions with an onium saltleach solution in order to cause dissolution of nickel and cobalt valuescontained in said material after which said nickel and cobalt containingleach solution is separated from undissolved residue and said separatedsolution is subjected to a cobalt removal operation in which saidseparated solutionv is treated with a sulphidizing agent topreferentially precipitate cobalt-values therefrom so {as to provide aproduct liquor and a product precipitate composed of a mixednickel-cobalt sulphide, said product liquor containing the bulk of thenickel values previously in said nickel and cobalt containing leachsolution together withna resualquantity of. cobalt, said productprecipitate coning..z.the.z;bulktof' the. cobalt values previouslyinsaidi -.-cohalt..containing leach solution togeer with .a. quantity.of cor-precipitated nickel, the improvem nt to. said.. =.eh p trf eiisvsl ,QP Q whereby the nickel--.cohalt.4 onin.-.said ..produc.t' liquoris adjusted to a value above about 7002i concurrently with an adjustmentof the nickel-cobalt ratio in said product precipitate to a value belowabout 2:1, saidwimprovement comprising the steps of: passing saidseparated nickel and cobalt containing leach solution to a firstcobalt-removal stage to which isadded sulphidizing agent in. controlledamount such as tocau'se formation offa. mixed]nickel cobaltisulphideprecipitate having a nickel cohalt ratio of less thanahout 2:1, removingfrom said first cobalt removal stage the mixed nickel-cobalt sulphideprecipitate formed therein and recycling a portion FORM PC4050 (10-59)uscoMM-oc 60376-P69 U.Sw GOVERNMENT PRINTING CFFICE: l5, 0-365-35, Y

lTJiiBER 3fil6fil8 PAGE I ll thereof te eeid first eobelt rmovel eteqeeed recovering the remainder thereof as eeid prodeot precipitateremoving eoletiern from eeid firet coloelt-removel eteee and recycling eportisrm thereet to eeid leeching operation and peeeieg the remeiederthereof e eeooed cobalt removal stage to which is added eelphidizinqagent in con-.- trolled amount each that the ratio of nickel to cobalttemeieiog in solution followieq formation of a mixed nickelcobaltsulphide precipitate therein :ie etove about ?@@sl, removing solutionfrom said second eobelteremovel eteee and recovery thereof axe eeidpreduct liqoer for subsequent treemeet for recovery of nickel therefromremoving from eeid second cobalt-removal etaqe time mired nickel cobelteulpl'aide precipitate termed thereio and recycling at least a portionthereof to eeid second cobalt remvel stage and adding any unrecyoledeortion thereof to said first cobaltremovel stage. .9

(Belem m eeiieel claim 4' end eubetitute the follewinq:

4. In a proceee for tree-ting nickel and cotelt bearing meteriel inwhich the material is eubjeoted to a leeching operation in which it isleached in at least two eteqes under oxidizing conditions-with eraammonium eelt leecheolu'tion in otderto cauee dieeolution of nitlkel'and cobalt; values contained in said material after which eid nickel.and cm'abatl'li containing leach solution from each said leaching etageis eepareted from 'undiseolved residue end said separated solution fromeach eaid leaching stage is: subjected to a cobalt removal operation inwhieh eeid separated solution ie treated witha eulphidizing agent topreferentially precipitate cobalt values therefrom eo as to provide aproduct liquor and a product precipitate composed of a mixednickel-cobalt sulphide; eeid product liquor containing the bulk wthenickel veloee previously in said nickel and cobalt containing leeolisolution together with a email residual quantity of cobalt eeid prodeetprecipitate containing tire hull: of the cobalt values previously insaid nickel and cobalt eontaininq leach solution-together with aquantity of co preoipitated nickel, the improvement to saidcobaltremoval operation whereby the nickel-cobalt ratio in said productliquor is adjusted to a value above about 700:1 concurrently with anadjustment of the nickel-cobalt ratio in said product precipitate to avalue below about 2:1, said improvement comprising the etepe of: peeeingnickel and cobalt containing solution eepereted from one said leachingstage to a first cobalt=removel etege to which is added sulphidizingagent in controlled amount such that the ratio E'KTENT NZJMBER I 3,7l66l8 PAGE III of nickel to cobalt remaining in solution followingformation of a mixed nickel cobalt sulphide precipitate therein is aboveabout 760:1 removing solution from said first cobalt-removal stage andrecovery thereof as said product liquor for subsequent treatment forrecovery of nickel therefrom, removing from said first cobalt-removalstage the mixed nickel cobalt sulphide precipitate formed therein andrecycling at least a portion thereof to said first cobalt-removal stageand adding any unrecycled portion thereof to a second ceia'balt removalstage; passing nickel and cobalt containing solution separated fromanother said leaching stage to said second cobalt removal stage to whichis added sulphidizing agent in controlled amount such as to causeformation of a mixed nickel cobalt sulphide precipitate having anickel-cobaltjratio of less than. about 2:1 removing from said secondcobalt removal stage the mixed nickel cobalt sulphide precipitate formedtherein and recycling a portion thereof to said second cobalt-removalstage and recovering the [remainder thereof as said product precipitate,renwving solution from said second cobalt-removal stage and recyclingthereof to said leaching operation, w a

Signed and sealed this 20th day of November 1973.

(SEAL) Attest:

EDWARD mmrs'rcasm se inns in T EGTMEYE 'Attesting Officer ActingComissioner sea-e

1. In a process for treating nickel and cobalt bearing material in whichthe material is subjected to a leaching operation in which it is leachedin one or more stages under oxidizing conditions with an ammonium saltleach solution in order to cause dissolution of nickel and cobalt valuescontained in said material after which said nickel and cobalt containingleach solution is separated from undissolved residue and said separatedsolution is subjected to a cobalt removal operation in which saidseparated solution is treated with a sulphidizing agent topreferentially precipitate cobalt values therefrom so as to provide aproduct liquor and a product precipitate composed of a mixednickel-cobalt sulphide, said product liquor containing the bulk of thenickel values previously in said nickel and cobalt containing in whichit is leached in at least two stAges under oxidizing conditions with anammonium salt leach solution in order to cause dissolution of nickel andcobalt values contained in said material after which said nickel andcobalt containing leach solution from each said leaching stage isseparated from undissolved residue and said separated solution from eachsaid leaching stage is subjected to a cobalt removal operation in whichsaid separated solu-tion is treated with a sulphidizing agent topreferentially precipitate cobalt values therefrom so as to provide aproduct liquor and a product precipitate composed of a mixednickel-cobalt sulphide, said product liquor containing the bulk of thenickel values previously in said nickel and cobalt containing leachsolution together with a small residual quantity of cobalt, said productprecipitate containing the bulk of the cobalt values previously in saidnickel and cobalt containing leach solution together with a quantity ofco-precipitated nickel, the improvement to said cobalt-removal operationwhereby the nickel-cobalt ratio in said product liquor is adjusted to avalue above about 700:1 concurrently with an adjustment of thenickel-cobalt ratio in said product precipitate to a value below about2:1, said improvement comprising the steps of: passing nickel and cobaltcontaining solution separated from one said leaching stage to a firstcobalt-removal stage to which is added sulphidizing agent in controlledamount such that the ratio of nickel to cobalt remaining in solutionfollowing formation of a mixed nickel-cobalt sulphide precipitatetherein is above about 700:1, removing solution from said firstcobalt-removal stage and recovery thereof as said product liquor forsubsequent treatment for recovery of nickel therefrom, removing fromsaid first cobalt-removal stage the mixed nickel-cobalt sulphideprecipitate formed therein and recycling at least a portion thereof tosaid first leach solution together with a small residual quantity ofcobalt, said product precipitate containing the bulk of the cobaltvalues previously in said nickel and cobalt containing leach solutiontogether with a quantity of co-precipitated nickel, the improvement tosaid cobalt-removal operation whereby the nickel-cobalt ratio in saidproduct liquor is adjusted to a value above about 700:1 concurrentlywith an adjustment of the nickel-cobalt ratio in said productprecipitate to a value below about 2:1, said improvement comprising thesteps of: passing said separated nickel and cobalt containing leachsolution to a first cobalt-removal stage to which is added sulphidizingagent in controlled amount such as to cause formation of a mixednickel-cobalt sulphide precipitate having a nickel-cobalt ratio of lessthan about 2:1, removing from said first cobalt removal stage the mixednickel-cobalt sulphide precipitate formed therein and recycling aportion thereof to said first cobalt removal stage and recovering theremainder thereof as said product precipitate, removing solution fromsaid first cobalt-removal stage and recycling a portion thereof to saidleaching operation and passing the remainder thereof to a second cobaltremoval stage to which is added sulphidizing agent in controlled amountsuch that the ratio of nickel to cobalt remaining in solution followingformation of a mixed nickel-cobalt sulphide precipitate therein is aboveabout 700:1, removing solution from said second cobalt-removal stage andrecovery thereof as said product liquor for subsequent treatment forrecovery of nickel therefrom, removing from said second cobalt-removalstage the mixed nickel-cobalt sulphide precipitate formed therein andrecycling at least a portion thereof to said second cobalt-removal stageand adding any unrecycled portion thereof to said first cobalt-removalstage.
 2. The process as claimed in claim 1, wherein said product liquoris maintained at a temperature of about 65* to 75* C. for a timesufficient to precipitate contained sulphides and any maNganese thencesaid precipitated sulphides and any manganese are separated fromsolution.
 3. The process as claimed in claim 1, wherein said mixednickel-cobalt sulphide product is washed with ammonium carbonate and thewash solution is recycled to the leaching operation.
 4. In a process fortreating nickel and cobalt bearing material in which the material issubjected to a leaching operation cobalt-removal stage and adding anyunrecycled portion thereof to a second cobalt-removal stage, passingnickel and cobalt containing solution separated from another saidleaching stage to said second cobalt-removal stage to which is addedsulphidizing agent in controlled amount such as to cause formation of amixed nickel-cobalt sulphide precipitate having a nickel-cobalt ratio ofless than about 2:1, removing from said second cobalt-removal stage themixed nickel cobalt sulphide precipitate formed therein and recycling aportion thereof to said second cobalt-removal stage and recovering theremainder thereof as said product precipitate, removing solution fromsaid second cobalt-removal stage and recycling thereof to said leachingoperation.
 5. In a process for treating nickel and cobalt bearingmaterial in which the material is subjected to a leaching operation inwhich it is leached in at least two stages under oxidizing conditionswith an ammonium salt leach solution in order to cause dissolution ofnickel and cobalt values contained in said material after which saidnickel and cobalt containing leach solution from each said leachingstage is separated from undissolved residue and said separated solutionfrom each said leaching stage is subjected to a cobalt-removal operationin which said separated solution is treated with a sulphidizing agent topreferentially precipitate cobalt values therefrom so as to provide aproduct liquor and a product precipitate composed of a mixednickel-cobalt sulphide, said product liquor containing the bulk of thenickel values previously in said nickel and cobalt containing leachsolution together with a small residual quantity of cobalt, said productprecipitate containing the bulk of the cobalt values previously in saidnickel and cobalt containing leach solution together with a quantity ofco-precipitated nickel, the improvement to said cobalt-removal operationwhereby the nickel-cobalt ratio in said product liquor is adjusted to avalue above about 700:1 concurrently with an adjustment of thenickel-cobalt ratio in said product precipitate to a value below about2:1, said improvement comprising the steps of: passing nickel and cobaltcontaining solution separated from one said leaching stage to a firstcobalt-removal stage to which is added sulphidizing agent to causeformation of a mixed nickel-cobalt sulphide precipitate therein,removing from said first cobalt-removal stage the mixed nickel-cobaltsulphide precipitate formed therein and recycling at least a portionthereof to said first cobalt-removal stage and adding any unrecycledportion thereof to a third cobalt-removal stage, passing solutionremoved from said first removal state to a second cobalt-removal stageto which is added sulphidizing agent in controlled amount such that theratio of nickel to cobalt remaining in solution following formation of amixed nickel-cobalt sulphide precipitate therein is above about 700:1,removing solution from said second cobalt-removal stage and recoverythereof as said product liquor for subsequent treatment for recovery ofnickel therefrom, removing from said second cobalt-removal stage themixed nickel-cobalt sulphide precipitate formed therein and recycling atleast a portion thereof to said second cobalt-removal stage and addingany unrecycled portion thereof to said first cobalt-removal stage,passing nickel and cobalt containing solution separated from anothersaid leaching stage to said third cobalt-removal stage to which is addedsulphidizing agent in controlled amount such as to cause formation of amixed nickel-coBalt sulphide precipitate having a nickel-cobalt ratio ofless than about 2:1, removing from said third cobalt-removal stage themixed nickel-cobalt sulphide precipitate formed therein and recycling aportion thereof to said third cobalt-removal stage and recovering theremainder thereof as said product precipitate, removing solution fromsaid third cobalt-removal stage and recycling thereof to said leachingoperation.
 6. The process as claimed in claim 4 wherein said productliquor is maintained at a temperature of about 65* to 75* C. for a timesufficient to precipitate contained sulphides and any manganese thencesaid precipitated sulphides and any manganese are separated fromsolution.